The off set is the distance between the center of the steering stem and the center of the fork legs.

A larger off set of course increases the wheel base where a smaller one shortens it. The smaller the off set the faster the bike will turn. This can also be adjusted by the rake of the forks but this means using off set yoke and stems.

The steeper the rake the faster the bike will turn. This is what happens when you lower the forks though the yokes, you are making the rake steeper.
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If I have to take the carbs off once more...